1. Field of the Invention
The present invention relates to acoustic microscopes, and more particularly to an acoustic microscope which includes means for holding an acoustic propagation medium.
2. Description of the Prior Art
First, the operating principle of an acoustic microscope will be briefly explained with reference to FIG. 1. An electric signal is produced by a pulse generator 1. The electric signal is converted into an ultrasonic wave 4 by a piezoelectric film 3 which is disposed on the upper surface of a spherical lens 2. The ultrasonic wave 4 is propagated within the spherical lens 2 and is directed by a spherical portion 2' so as to be focused on a specimen 5. The ultrasonic wave having impinged on the specimen 5 is reflected by the surface and interior of the specimen, to become an ultrasonic echo having information relating to the specimen. Tracing the same path reversely, the echo reaches the piezoelectric film 3 and is converted into an electric signal. In order to send this signal to a monitor 6 through a receiver 19 and to form a two-dimensional picture on the monitor 6, the specimen 5 on a specimen holder 20 is scanned at high speed and little by little in the horizontal direction by movement of X- and Y-stages 7, 7' while the above operations are being repeated. On this occasion, a medium 8 functions to efficiently propagate the ultrasonic wave between the spherical lens 2 and the specimen 5 without allowing it to get out.
As illustrated in FIGS. 1 and 2, the medium (for example, water) 8 in the prior-art acoustic microscope has been held between the lens 2 and the specimen 5 by surface tension. The water has been supplied by hand employing a syringe 9 as shown in FIG. 2, and has been drained by blowing it away with air. These methods have the following disadvantages:
1. In relation to the principle of the acoustic microscope, when the specimen 5 is scanned, the water 8 is sometimes sprung out to cause a deficiency of the water.
In the case of observing the specimen with the acoustic microscope, the scanning width of the specimen is greater and the relative speed of movement between the specimen 5 and the spherical lens 2 is higher when a larger area is observed at a lower magnification. The deficiency of the water is prone to occur at such time.
2. Since the water is supplied by hand, the specimen 5 might be damaged by the tip of the needle 9' of the syringe 9.
3. The water 8 blown away by the air during the drainage scatters to stain the specimen and the surrounding mechanism portions.
4. The supply and drainage of the water attendant upon the exchange of the specimen 5 or upon the movement of the specimen 5 for changing the place thereof to be observed are troublesome.